1. Field of the Invention
This invention relates generally to a diaphragm for a loudspeaker and, more particularly, to a diaphragm for a loudspeaker having a high internal energy loss.
2. Description of the Prior Art
In general, a diaphragm for an electro acoustic transducer such as a loudspeaker should have a large ratio of modulus of elasticity E to density .rho. (E/.rho.) thereof so as to increase its range of motion in the direction of the piston or bobbin. Further, in order to have a relatively smooth frequency characteristic in the high frequency region, the diaphragm should have a suitable internal energy loss.
It is generally known that a diaphragm with a honeycomb core structure has a relatively large ratio of modulus of elasticity to density E/.rho.. Such diaphragms are typically formed of a pair of parallel sheet members made from, for example, aluminum, beryllium or other metal foil or a carbon or other (FRP) fiber reinforced plastic (CFRP) with a honeycomb core member made of, for example, aluminium foil, is sandwiched between the sheet members. Such a diaphragm is generally lightweight with a high rigidity, that is, the ratio of modulus of elasticity to density E/.rho., is high. However, it has a small internal energy loss. Therefore, it has a high resonance sharpness in the high frequency band. Thus, it is seen that it becomes very difficult to satisfy all of the above conditions of low density, high rigidity and high internal energy loss in a diaphragm of the type having a honeycomb core structure.